Router is playing important role in Single Page Application (SPA). It is getting & applying the Partials/Views/Templates into corresponding places. Also, using this technique, navigation between one view to another view is performed.
> ngRoute is a angular core module which is good for basic scenarios. I believe that they will add more powerful features in upcoming releases.
> Ui-router is a contributed module which is overcome the problems of ngRoute. Mainly Nested/Complex views.
Some of the difference between ui-router and ngRoute
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